1. Field of the Invention
This invention relates generally to a method of purifying biological compounds or molecules, such as polypeptides, by crystallization. More particularly, the compounds can be purified to a significantly higher degree of purity than previously available techniques. In another embodiment, the present invention relates to crystallizing biological compounds on nucleating agents with a close lattice match to the crystalline lattice of the biological compound to selectively obtain biological compound crystals of high purity in a high yield.
2. Background Art
Crystallization of biological compounds, such as polypeptides, is important, both as one of the final separation or purification steps in bioprocessing and for growing crystals for basic scientific studies, such as structural analysis by X-ray diffraction. For example, improvements in protein purity are important to achieve more therapeutically acceptable proteins for drug use and for facilitating or even permitting the study of proteins by, for example, X-ray diffraction for rational drug design. Traditional methods for crystallizing proteins (herein after referred to as polypeptides), such as by spontaneous crystallization wherein no nucleation agent is used, have resulted in high failure rates and high heterogeneity of any resulting crystals. The present invention provides techniques for obtaining biological compound crystals in higher purity than previously attained, or in a combination of a high purity in a high yield never before attainable, based on their attachment to an exogenous nucleating agent.
This invention, therefore, represents a new method of growing biological compound crystals, such as polypeptide crystals, of high purity, and solves a need in the art for producing crystals of high purity, and in one embodiment, in a high purity and in a high yield.